Symbiosis, defined as the living together of two or more organisms in close or intimate association, is often a mutually beneficial interaction between two organisms. Most plants are symbiotic with fungi (Petrini, 1986) and these fungi play important roles in the structure, function, and health and adaptation of plant communities (Bacon and Hill, 1996; Clay and Holah, 1999; Petrini, 1986; Read, 1999; Rodriguez and Redman, 1997).
It has been demonstrated that a symbiotic relationships with fungi can enhance the growth of host plants under stressful conditions. For example, specific strains of endophytic fungi confer tolerance to host plants against extreme environmental conditions including temperature, drought, and salinity (Redman et al., 2002b; Rodriguez et al., 2004; Rodriguez and Redman, 2008; Rodriguez et al., 2009; Redman et al., 2011; Rodriguez et al., 2012). Endophytes are a class of fungal symbionts that reside within host plant roots, stems and/or leaves. In addition to promoting stress tolerance, endophytes also increase nutrient acquisition and growth rates (biomass and yields) of host plants, and improve water use efficiency (Rodriguez et al., 2008; Rodriguez et al., 2009).
Abiotic stresses (such as drought, temperature, salinity, pH and nutrient) alter the physiology of plants resulting in decreased fitness, health, development and yields. Propagating plants under marginal growth conditions (typically due to abiotic stresses) would allow for an increase in agriculture production and mitigation of climate induced habitat changes for both crop and native plants. Moreover, creating new vegetation is important for soil and water remediation of polluted sites created by modern industry and other human activities.
Previous published studies (Redman et al., 2002b & 2011; Rodriguez et al., 2008 & 2012) have demonstrated that a special class of fungal symbionts (class 2) can confer biotic and abiotic stress benefits to plants simply by colonizing them with the fungal endophyte.